Respiratory and bloodstream coinfections and antimicrobial use in hospitalised patients with moderate to severe COVID-19: An Australian retrospective cohort study

Laura Frederiksen; Shradha Subedi; Keat Choong; James Anderson; Timothy Baird

doi:10.1371/journal.pone.0352344

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Respiratory and bloodstream coinfections and antimicrobial use in hospitalised patients with moderate to severe COVID-19: An Australian retrospective cohort study

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Respiratory and bloodstream coinfections and antimicrobial use in hospitalised patients with moderate to severe COVID-19: An Australian retrospective cohort study

Laura Frederiksen, Shradha Subedi, Keat Choong, James Anderson and Timothy Baird

PLoS One, Vol.21(7), pp.1-12

2026

DOI: https://doi.org/10.1371/journal.pone.0352344

PMCID: PMC13340816

PMID: 42412874

Appears in COVID-19 Research

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Abstract

Co-infections

COVID 19

Respiratory infections

Virus testing

Antibiotics

Nosocomial infections

Intensive care units

Medical risk factors

Background COVID-19 remains a leading infectious cause of death and hospitalisation globally. Coinfections with SARS-CoV-2 and other respiratory pathogens may result in more severe illness, however the prevalence of coinfection in Australia is unknown. Aims This Australian study aimed to determine the prevalence and microbiology of respiratory and bloodstream coinfections, antimicrobial use, and outcomes in hospitalised patients with moderate to severe COVID-19. Methods This was a retrospective cohort study of adult patients with moderate to severe COVID-19, admitted at the Sunshine Coast University Hospital from February to July 2022. Data regarding patient characteristics, comorbidities, microbiological results, hospital length of stay, intensive care unit admission, and mortality were compared between the coinfection and no-coinfection groups. Logistic regression analysis was performed to identify factors associated with coinfection. Results Coinfection was documented in 23 (12%) of the 190 patients admitted with moderate-severe COVID-19. Bacterial infections were the most common (54% of coinfection episodes), followed by fungal (32%), and viral (14%). Antibiotics were prescribed for 74% of patients, for a median duration of 6 days (IQR 4–8 days). Patients with coinfection had a median length of stay of 9 days (IQR: 4–19.5) compared to 6 days in the no-coinfection group (IQR: 3–9; p = 0.047). There was no mortality difference between the two groups. Patients admitted to intensive care had higher odds of coinfection compared to patients not admitted to intensive care (OR 3.39, 95% CI 1.19–9.66, p = 0.02). Severe COVID-19 and Aboriginal and Torres Strait Islander descent were also associated with coinfection. The causal nature of these relationships requires further interrogation. Conclusions The prevalence of respiratory and bloodstream coinfection was low in our cohort of hospitalised COVID-19 patients. Despite non-standardised microbiological testing, antibiotic use was disproportionately high. Further work is required to define risk factors and improve diagnosis of COVID-19-associated coinfection, to better inform antimicrobial stewardship.

Details

Title: Respiratory and bloodstream coinfections and antimicrobial use in hospitalised patients with moderate to severe COVID-19: An Australian retrospective cohort study
Authors: Laura Frederiksen (Corresponding Author) - The University of Queensland
Shradha Subedi - The University of Queensland
Keat Choong - Griffith University
James Anderson - Griffith University
Timothy Baird - University of the Sunshine Coast
Publication details: PLoS One, Vol.21(7), pp.1-12
Publisher: Public Library of Science
Date published: 2026
DOI: 10.1371/journal.pone.0352344
ISSN: 1932-6203
PMID: 42412874; PMC13340816
Copyright note: © 2026 Frederiksen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Organisation Unit: School of Science, Technology and Engineering; Centre for Bioinnovation
Language: English
Record Identifier: 991246170002621
Output Type: Journal article

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